Conventionally, wafer level packaging technique such as Chip Scale Package (hereinafter, called as “CSP”) has been proposed. In the wafer level packaging technique, a resin for protecting the surface of each semiconductor chip is applied on a semiconductor wafer and the electrode pads for each semiconductor chip are also provided on the semiconductor wafer so as to form a semiconductor wafer assembly. Then, the semiconductor wafer assembly is divided into semiconductor electronic component packages. Concretely, a first insulating film is formed on a semiconductor wafer with electrode pads thereon so that the electrode pads can be exposed. Then, a redistribution layer is formed and a second insulating layer is formed. Then, mounting pads are formed on the second insulating layer so as to be electrically connected with the redistribution layer through the opening of the second insulating layer, and solder balls are formed on the mounting pads, respectively. Then, the thus obtained semiconductor wafer assembly is divided into semiconductor electronic component packages (JP-B 3970849 (PATENT)).
However, the above-described wafer level packaging technique requires photolithography technique in the exposure of the electrode pads through the first insulating layer, the patterning of the redistribution layer and the formation of the mounting pads through the opening of the second insulating layer. In other words, in order to electrically connect the electrode pads of each semiconductor chip (each electronic component) and the mounting pads, respectively, it is required to partially remove the first insulating layer and the second insulating layer between the electrode pads and the mounting pads.
In this point of view, if some convex-concave portions are formed on the semiconductor wafer, the resist layer can not formed uniformly so that the developing can not be carried out uniformly through the resist layer. As a result, the photolithography can not be carried out under good condition and thus, the intended electronic component packages can not be obtained.